I have always had 38 front and back on all my cars.
Having ridden (and still riding) motorcycles for a long time I have always been a bit pedantic when it comes to pressures. I check them once a week and always when the tyres are cold and NEVER rely on the gauge up the pump to be accurate. Spend a few bucks and buy your own pressure gauge and leave it in the boot/glove box!
You would be surprised how inaccurate the servo gauges are. I have seen them out up to 10 PSI!
As has been mentioned in a prior post, it is somewhat up to personal preference though. As long as you are around 36 - 40 you will be fine.